Electronic air filters having conductive polarizing screens are well known and are described in a number of patents including U.S. Pat. No. 4,549,877, Canadian patents no. 1,272,453 and no. 2,270,976, and Canadian patent applications no. 2,635,729 and no. 2,421,435 The U.S. patent describes a pair of outer hinged screens for enclosing a pair of glass fibre pads between which a grid made up of coarse wire mesh is located. The outer screens are grounded while the grid is charged to about 7 kv, with resulting polarization of the glass fibres and agglomeration and entrapment of air-borne particles in the air which flow through the screens.
Existing electronic air filters have many shortcomings of which the production of ozone may be the most serious. Ozone is a highly undesirable by-product of the electronic filtering process, not only because of its pungent unpleasant odour but because of its toxicity. Another shortcoming of known electronic air filters is that a relatively large amount of power is required for the filters to operate effectively. An additional shortcoming is that the wires within the filter occupy a significant portion of the passageway for the flow of air through the filters and as a result restrict the volume of air that is filtered.
I have invented an, electronic air filter which overcomes or substantially reduces those shortcomings. My air filter requires a voltage lower than is generally required to create a corona field around a grid for polarizing the grid with resulting production of relatively little ozone. Moreover, incorporated into the grid of my air filter are strips of carbonaceous material which function to absorb much of the volatile organic compounds in the air which flow through the filter.
As far as power consumption and restriction of air flow are concerned, the grid within the filter of my invention is made up largely of electrically conductive filaments of small diameter. Not only do the filaments consume less power than the wires in most conventional electronic air filters but they occupy less space and accordingly allow more air to flow through the filter with a resulting increase in the efficiency of the electronic filtering process.